Improve Docker image

[To-om]

Request Type

Enhancement

Work Environment

Cortex 3.1.0-RC1

Description

The aim of this issue is to improve docker image:

• Cortex can use docker of the host or docker in docker
• Fix permission problem on docker socket (Update docker.sbt + entrypoint to fix 3.1.0-0.1RC1 #285). Docker entrypoint run with root and before switching to cortex user, chmod the socket file
• Fix job directory mapping by adding the parameters --job-directory and --docker-job-directory
• All entrypoint parameters can be set using environment variable. This make docker-compose file more readable.